Aerodynamics can play an important role in cycling events such as races and time trials. At race speeds, aerodynamic drag may account for up to 90% of the total resistance. A significant portion of the energy expended by a racer is used to overcome this drag, and efforts have been made to reduce drag caused by the rider's gear as well as the bike itself.
Previous efforts to reduce the drag caused by air moving over and around a riders head have resulted in a time trial (TT) helmets that are much larger than other types of helmets. Conventional TT helmets often have teardrop shapes, with elongated, tapering tails to facilitate the orderly flow of air over the helmet and rider while minimizing drag. However, this reduction in drag often comes at the cost of increased weight, discomfort, and unwieldiness. Furthermore, the long tail of conventional TT helmets may become an aerodynamic liability when the wearer's head is turned or when there is a crosswind. Additionally, the use of conventional TT helmets is sometimes restricted; for example, in some stage races, conventional TT helmets are prohibited, in part due to the danger they pose to other riders.